The Zoo Employee is a janitor at the San Diego Zoo who informs Ross about the real whereabouts of Marcel, after the zoo administrator told Ross that he had died. He's portrayed by Dan Castellaneta, who is best known for providing the voice of Homer Simpson, Krusty the Clown, Barney Gumble, among many others on the FOX animated series The Simpsons.
The Zoo Employee is an odd man with a strange fascination for the animals in the zoo. He tells Ross that there was a break-in and Marcel was taken (along with a snowy egret, a two-toed sloth, and three hooded sweatshirts from the zoo gift shop) and that the story told to Ross is a big cover up because the zoo wants to avoid bad publicity. He tells Ross that the cover-up goes very high up, but is shocked to learn that Lipson knows.
His initial plan is to get Ross to bribe him, but tells Ross everything he knows too soon, thus failing.